Multiplying Fractions/Decimals Absent Copy 1/3,4

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# Multiplying Fractions/Decimals Absent Copy 1/3,4 - PowerPoint PPT Presentation

Multiplying Fractions/Decimals Absent Copy 1/3,4. Example 1. Multiply: write answer in simplest form. 3 • 7 4 9 3 • 7 = 21 4 • 9 36 Num. Denom. 21 36 7 • 3 2 • 2 • 3 • 3

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Presentation Transcript
Example 1
• Multiply: write answer in simplest form.

3 • 7

4 9

3 • 7 = 21

4 • 9 36

Num. Denom.

21 36

7 • 3 2 • 2 • 3 • 3

7 • 3

2 • 2 •3 • 3

Solution

• Do we need to get a common denom. when we multiply?
• YES or NO
• There are 2 ways to multiply.
• 1. You can multiply straight across.
• 2. You can cross reduce(only if you can) and then multiply across.
• Can we reduce are answer?
• YES or NO
• What do we make before reducing the answer?
• A T-chart

7

12

Example 2
• Multiply: write answer in simplest form.

-2 ¾(½)

-2 ¾ = -11

4

-11 • 1 = -11

4 2 8

-1 3/8

Solution

• What do we do first before multiplying?

We need to change the mixed fraction into an improper fraction.

• There are 2 ways to multiply.
• 1.You can multiply straight across.
• 2.You can cross reduce (only if you can) and then multiply across.
• Can we reduce are answer?
• YES or NO
• What question do we ask are selves. Hint: think about the 8.
• How many times does 8 go into 11 and how many are left over.
• What is the integer rule we use?
• A neg. # multiplied by a pos. # the answer is always Neg.

-1 3/8

Example 3
• Multiply:

-0.06(9.3)

-0.06

x9.3

018

+ 0540

0558

0.558

Solution

• How can we re-write this problem before multiplying?
• Stack the numbers on top of each other before you multiply.
• Do we need to line up the decimals when we multiply?

YES or NO

• After we multiply how many decimals places do we have to move in the answer?
• We have to move the decimal 3 places.
• Do we move the decimal left or right when making the final answer?
• We move the decimal to the left from the back of the answer.
• What is the integer rule we use?
• Neg. # multiplied by a pos. # is always a neg. answer.

-0.558

Example 4
• Multiply:

-6.7

x -0.8

536

+000

536

5.36

Solution

Solution

• After we multiply how many decimals places do we have to move in the answer?
• We have to move the decimal 2 places.
• Do we move the decimal left or right when making the final answer?
• We move the decimal to the left from the back of the answer.
• What is the integer rule we use?
• When multiplying a neg. # by a Neg. # the answer is always positive.

5.36